".Net" and "Common Language Runtime" refer specifically to Microsoft's implementation. The spec is called the "Common Language Infrastructure".

Wikipedia seems to use "Common Language Runtime" in both ways - the Mono article uses it in the generic sense, whereas the CLR's own article explicitly states that it refers to .Net's implementation.

.Net also has ngen.exe which isn't really JIT at all, it's traditional 'offline' ahead-of-time compilation. In a sense that's rather like the traditional Unix compile-and-install model. One sees the oxymoron "pre-JIT" used to describe this.

This is another difference from HotSpot, which historically never cached native code to disk, though other JVMs have always been able to do this (Excelsior Jet, and GCJ, for instance).

Apparently AOT may be coming to Java though - it may even already be here, I'm not quite sure.

https://www.infoq.com/news/2016/10/AOT-HotSpot-OpenJDK-9 , http://openjdk.java.net/jeps/295

I recall once reading that one of the reasons HotSpot didn't cache native code, was the issue of securing that cache. Not sure what they've done to address that, nor what .Net does; it seems a valid concern.

That's an interesting read re. Hejlsberg. Worth noting that Mono takes them up on that and does feature an interpreter.

Edit: I'm wrong about the terminology! https://news.ycombinator.com/item?id=15688290